Preset your focal distance

[Safety Stop]

I did a lot of reading about underwater photograhy (including the book of Martin Edge) and cant find the answer to my question. How can you preset your focal distance underwater for WA shoots?

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[deadbilly]

It's entirely dependent on what model of camera you use.

 

[fbk]

Assuming your camera will focus manually... you manually focus.

 

[Safety Stop]

Sorry, forgot to tell you that I'm using a Nikon D7100.

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[sharkbaitDAN]

There is probably not a very effective method before the dive, other than trial and error setting the focus manually, and then not using AF underwater.

During the dive, fixing the focal distance is very useful for WA video. My camera has an AF/AE lock button, which I have set to turn the AF on (like a half shutter press). when shooting video, I will use that button to focus on my subject and then start recording once focus is reached. The camera will not try to focus on its own during recording, so all I have to do is not hit the AF button. In addition, I use a Tokina 10-17, which has a huge depth of field, so even if I don't get focused exactly, or if my subject moves (it does occasionally happen underwater :shocked2 I don't miss the shot.

I haven't shot the D7100, but there should be a method to do something similar.

Hope this helps.

 

[Interceptor121]

You need to take into account that the book has been written with equipment that may not be current
The D7100 has a shutter lag of 297 ms even with the flash on that is very quick so the idea that you jump in the water with the lens preset at the hyperfocal distance may or not be relevant depending on the camera you have
In some cases with split shots for example the lens fails to focus when you have water and air at the same time so you want to lock focus

If you want to have the old school preset you need to go in to custom settings control f4 and choose AE mode AF ON
In this mode you have to press the AFAE lock button for the camera to focus as this disables the shutter autofocus entirely
The more normal mode to operate is to use the AEAF lock button in AF only and keep the lock button pressed until you pressed the shutter once you have focussed as desired however this does not work as a 'jump setting'

This split shot provide an example of presetting the focus 'on your foot'

Ras Katy Sunset by Interceptor121, on Flickr

 

[deeper thoughts]

Great picture

 

[Safety Stop]

Yes, super great shot with a big dome

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[ShootingUnderwater.com]

Hi,

I have set my lens to manual focus a few times for night diving. Specifically, for shooting manta rays on a night dive in Kona. I focused on something about 5' away. However, it's very trying because you must wait for the subject to enter the "sweet" spot before firing. I haven't tried this with other variables though.

 

[DazedAndConfuzed]

Not sure if 5' on the lens indicator will actually mean subject is 5' away, especially with additional refraction of water. Also, subject will look closer than it really is, which also depends on the subject's distance.

But to preset at a certain distance, you also have to calculate the depth of field at the f-stop you are going to take the picture at, and determine the allowable min/max subject distance. Old lenses has such indicator, new ones don't seem to because they assume the camera is going to be doing the focusing for you.